Updated efficacy and toxicity analysis of irinotecan and oxaliplatin (IROX) : intergroup trial N9741 in first-line treatment of metastatic colorectal cancer

BACKGROUND: Efficacy and toxicity of oxaliplatin (Eloxatin; Sanofi-Aventis, Paris, France) combined with irinotecan (IROX) were examined in 383 patients enrolled on the IROX arm of Intergroup Study N9741. METHODS: This IROX regimen was oxaliplatin 85 mg/m(2) and irinotecan 200 mg/m(2) administered every 3 weeks. The relation between adverse events on IROX to selected characteristics was analyzed. Time to progression (TTP), response rate, and overall survival for patients treated with IROX compared with patients treated with oxaliplatin with 5- fluorouracil (FOLFOX) were updated in this article. RESULTS: Grade >or=3 gastrointestinal and hematologic toxicities were common with 39% patients experiencing neutropenia, 28% diarrhea, and 21% vomiting. Patients ages >70 years experienced higher rates of grade >or=3 toxicity, with significantly higher rates of grade >or=3 hematologic toxicities (P = .02). Long-term toxicity was uncommon, and nearly all cases of grade >or=3 neurotoxicity resolved within 10 months. Fifty-two percent of patients required dose reductions for adverse events, and 26% experienced 119 hospitalizations related to complications of treatment or their disease, with 5 treatment-related deaths. This analysis confirmed prior findings that FOLFOX is superior to IROX in terms of response rate (43% vs 36%, p = 0.002), TTP (9.2 months vs 6.7 months, P < .0001), and overall survival (19.5 months vs 17.3 months, P = .0001). CONCLUSIONS: IROX was found to be less active than FOLFOX but with a similar toxicity profile except in patients ages >70 years. Although IROX may be considered in patients intolerant of 5-FU or in patients known to have a dihydropyrimidine dehydrogenase (DPD) deficiency, it should be used with caution in older patients.